Northern blot analysis shows that TCA3 is expressed after activation with either PMA/ionophore or high affinity IgE cross-linking in C57 cells. mRNA of TCA3 is induced within 2 hours, peaks at 3 hours, and disappears at 6 hours. Half-life of mRNA determined by adding actinomycin D is approximately 2 hours. These results suggest the TCA3 is regulated transcriptionally. Nuclear run-on assays show that the rate of TCA3 mRNA transcription is increased after activation consistent with transcriptional regulation. Promotor analysis demonstrated that the TCA3 gene is regulated transcriptionally in mast cells, and that the minimal promotor sequences are contained within the 0.082 kb upstream region of the TCA3 gene with a putative enhancer NF-kB element between -0.324 kb and -0.324 kb and -0.136 kb and a putative inhibitory element between 1.324 k and 2.0 kb upstream from transcription start site. Mast cells have also been transfected with a series of 5' deletion mutants of TNF-alpha cat constructs to study the regulation of TNF-alpha via FcepsilonRI crosslinking. Mast cells chemotax to the chemokines RANTES and MCAF in a dose-dependent manner. Parallel studies demonstrate that his chemotaxis is not accompanied by mast cell histamine release. When mast cells are activated through FcepsilonRI, chemotaxis can also be demonstrated to MIP-alpha, and PF-4.